1 files changed, 40 insertions, 0 deletions
diff --git a/include/mbgl/style/expression/parsing_context.hpp b/include/mbgl/style/expression/parsing_context.hpp
new file mode 100644
index 0000000000..7898da790d
--- /dev/null
+++ b/include/mbgl/style/expression/parsing_context.hpp
@@ -0,0 +1,40 @@
+#pragma once
+
+#include <string>
+#include <vector>
+#include <mbgl/util/optional.hpp>
+
+namespace mbgl {
+namespace style {
+namespace expression {
+
+class ParsingContext {
+public:
+    ParsingContext() {}
+    ParsingContext(ParsingContext previous,
+                   optional<size_t> index,
+                   optional<std::string> name) :
+                   path(previous.path),
+                   ancestors(previous.ancestors)
+    {
+        if (index) path.emplace_back(*index);
+        if (name) ancestors.emplace_back(*name);
+    }
+    
+    std::string key() const {
+        std::string result;
+        for(auto const& index : path) { result += "[" + std::to_string(index) + "]"; }
+        return result;
+    }
+    
+    std::string key(size_t lastIndex) const {
+        return key() + "[" + std::to_string(lastIndex) + "]";
+    }
+    
+    std::vector<size_t> path;
+    std::vector<std::string> ancestors;
+};
+
+} // namespace expression
+} // namespace style
+} // namespace mbgl